1. Field of the Invention
This invention relates to improved polymer blends comprising, a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon. More particularly, the invention relates to blends comprising the linear alternating polymer and a polyvinyl alcohol, such as ethylene vinyl alcohol.
The general class of polyketone polymers of carbon monoxide and olefin(s) has been known for some years. Brubaker, U.S. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initiators, such as peroxy compounds like benzoyl peroxide. British Patent 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium as catalyst. Nozaki extended the process to linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for exmaple, U.S. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and unsaturated hydrocarbons, e.g., ethylene or ethylene and propylene, has become of greater interest in part because of the greater availability of the polymers. These polymers, often referred to as polyketones or polyketone polymers, have been shown to be of the repeating formula --CO--(A)-- where A is the moiety of an ethylenically unsaturated hydrocarbon polymerized through the ethylenic unsaturation. For example, when the ethylenically unsaturated hydrocarbon is ethylene, the polymer is represented by the repeating formula --CO--(CH.sub.2 --CH.sub.2)--. The general process for the more recent production of such polymers is illustrated by a number of published European patent applications including 0,121,965 and 0,181,014. The process typically involves a catalyst composition formed from a compound of a Group VIII metal selected from palladium, cobalt or nickel, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of phosphorous, arsenic or antimony.
The resulting thermoplastic polymers having utility in the production of articles such as parts for the automotive industry, as structural members for use in the constructon industry, and as containers for the packaging industry.
Such shaped parts are produced by processing the polyketone according to known methods. For some applications it has been found desirable to provide a polymer composition having properties somewhat different from those of the polyketone polymers. It would be of advantage to retain the more desirable properties of the polyketone polymer and yet improve other properties. This advantage is often obtained through the provision of a polymer blend, with polyvinyl alcohol.
This invention also relates to a packaging material prepared from a blend of a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon with a polyvinyl alcohol, such as ethylene vinyl alcohol.
Polymer systems such as fully hydrolyzed polyvinyl alcohol have very high resistance to oxygen permeability, but these systems have serious deficiencies in that they are water sensitive and have a very high water vapor transmission rate. Furthermore, these polyvinyl alcohol polymers fail to retain their excellent resistance to oxygen permeability at conditions of high humidity, and, in general have poor processing characteristics, which precludes thermal processing into shaped articles. The poor thermal processability stems from the necessity of heating the resin above its melting point (180.degree. C. is the point at which polyvinyl alcohol decomposes) and under these conditions the resin undergoes thermal decomposition.
The currently available olefin/vinyl alcohol copolymers are characterized by a thermal processing behavior and barrier properties which limits their utility as packaging materials. Notable among these deficiencies is the tendency of the resin to develop gel specks and/or burn spots during the extrusion process. Furthermore, the broad distribution of olefin content in the available olefin/vinyl alcohol resins results in poor water vapor transmission rate (WVTR) properties.
A definite need exists for a blend material which has a high resistance to oxygen permeability and a low water vapor transmission rate as well as improved processing and physical properties to allow their fabrication into diverse shapes and sizes, e.g., bottles, containers, sheets, thin films, etc.
It is therefore an object of this invention to provide a novel packaging materials for foods, medicines, and related objects, wherein the packaging materials exhibit a high resistance to oxygen permeability and a low water vapor transmission as well as improved processing and physical properties.
It is a further object of this invention to provide for foods, medicines, and other related substances, a novel packaging material which exhibits high resistance to oxygen permeability and a low water vapor transmission rate as well as improved processing and physical properties.
These and other objects are obtained by providing a novel blend, such as for packaging materials for foods, medicines and other related substances, which comprises (i) a lower .alpha.-olefin/vinyl alcohol copolymer wherein the vinyl alcohol is between 30 to 50% by weight, and the residual non-hydrolyzed fraction of the vinyl alcohol portion is below 3.0-15%; and (ii) a novel polyketone polymer.